The present invention relates to fiber optic connectors. The invention relates more particularly to fiber optic connectors that can be mounted on a circuit board, backplane, or other panel, and that are compatible with standard adapters and other fixtures such as polishing fixtures that are commonly used.
Fiber optic connectors are attached at to ends of optical fibers to enable one or more optical fibers to be optically coupled with one or more other optical fibers of another connector or other optical transmission device. A fiber optic connector generally includes a housing in which a forwardly projecting ferrule is mounted. Usually, one or more optical fibers pass through the ferrule and have ends that are flush with or project slightly beyond the forward end of the ferrule for coupling with the end of one or more other optical fibers in a complementary fiber optic connector or device. The housing of the connector typically includes features for locking the connector in engagement with the complementary connector or device.
In some applications, it is desirable to mount a fiber optic connector on a circuit board, backplane, or other panel. Various panel-mountable fiber optic connectors have been developed. U.S. Pat. No. 5,245,683 shows one such panel-mounted connector, comprising a housing, a cylindrical ferrule, and a ferrule holder adapted to be secured around the ferrule. The ferrule holder has a flange and the housing has a rearwardly facing shoulder against which the flange of the ferrule holder abuts when the ferrule holder is inserted through the rear end of the housing. A spring is inserted into the rear end of the housing behind the ferrule holder, and the spring engages the flange of the ferrule holder. The legs of a U-shaped spring-retaining clip are inserted transversely into the housing through openings therein for holding the spring in a compressed position so that the spring biases the ferrule holder and ferrule forwardly. The spring allows the ferrule to xe2x80x9cfloatxe2x80x9d to facilitate close coupling of the ferrule with the ferrule of another connector. The housing is molded of plastic and has a pair of integrally formed projecting pegs for inserting into holes in a circuit board to mount the connector on the board. The spring-retaining clip can be removed while the connector remains mounted on the board, so that the ferrule holder and ferrule can be removed from the housing for repair or replacement.
Another type of panel-mounted connector that is commercially available is an SC compatible connector that has a ferrule holder that can be oriented in one of four different positions rotationally displaced from one another about the axis of the ferrule for xe2x80x9ctuningxe2x80x9d the direction of the concentricity of the optical fiber in the ferrule with respect to the housing of the connector. A disadvantage of this connector is that the ferrule concentricity angle cannot always be optimized, and thus the insertion loss cannot always be minimized. Another disadvantage of this connector is that it is not compatible with standard automated SC polishing fixtures that are used for other SC connectors, and hence the ferrule must be manually polished.
The present invention addresses the above needs by providing a panel-mounted (or board-mounted) fiber optic connector that, in preferred embodiments of the invention, can be used in automated polishing fixtures and is compatible with standard adapters. The connector preferably also includes a xe2x80x9cpre-tunedxe2x80x9d ferrule holder and ferrule assembly whose concentricity angle is in a predetermined orientation, the ferrule holder being mountable in the connector in only one orientation so that the concentricity angle is always in a predetermined orientation relative to the connector.
To these ends, a fiber optic connector in accordance with one preferred embodiment of the invention comprises an outer housing defining an interior passage extending longitudinally therethrough, and at least one mounting element connected with the outer housing for mounting the connector onto a panel. The connector also includes a connector insert subassembly inserted through the rear end of the outer housing into the interior passage thereof. The connector insert subassembly is slidable longitudinally within the outer housing, and comprises an inner housing defining an inner passage extending longitudinally therethrough, and a ferrule holder, ferrule, and a spring mounted within the inner passage of the inner housing. A compression spring is inserted into the rear end of the outer housing abutting the connector insert subassembly, and a spring retainer is inserted into the outer housing behind the compression spring to capture the spring in a compressed condition so as to cause the spring to bias the connector insert subassembly forwardly against a stop defined by the outer housing.
Preferably, the ferrule holder and ferrule are slidable as a unit in the longitudinal direction within the inner housing, and the connector insert subassembly further comprises a ferrule spring and a member connected with the inner housing for compressing the ferrule spring between the member and the ferrule holder such that the ferrule spring biases the ferrule holder forwardly against a stop defined by the inner housing. A forward portion of the ferrule preferably projects longitudinally forward out a forward end of the inner housing when the ferrule holder is biased forward by the ferrule spring against the stop of the inner housing. The forward end of the inner housing preferably also projects longitudinally forward out the forward end of the outer housing when the connector insert subassembly is biased forward by the compression spring against the stop of the outer housing.
In the preferred embodiment of the invention, the outer housing defines openings through opposite side walls thereof, and the inner housing includes projections that are accessible through the openings in the outer housing for engagement with resilient fixing members of a polishing fixture. Thus, the connector can be inserted into the polishing fixture of polishing apparatus until the resilient fixing members of the polishing fixture engage the projections on the inner housing of the connector, thereby securing the connector in the fixture. The outer housing preferably also includes ramp surfaces proximate the openings through the side walls thereof, the ramp surfaces sloping outwardly away from a central longitudinal axis of the connector in the forward longitudinal direction such that pulling rearwardly on the outer housing causes the ramp surfaces to move the resilient fixing members of the polishing fixture outwardly to disengage the projections on the inner housing so that the connector can be removed from the fixture.
The spring retainer and the outer housing preferably are structured and arranged such that the spring retainer is inserted into the rear end of the outer housing in the forward longitudinal direction until cooperative retaining elements formed on the spring retainer and the outer housing engage each other to fix the spring retainer in the longitudinal direction. The retaining elements comprise one or more resilient projections formed on one of the spring retainer and the outer housing, and one or more recesses formed in the other of the spring retainer and the outer housing for receiving the resilient projection(s). Preferably, the spring retainer has the projection(s) and the outer housing has one or more openings therethrough so that the spring retainer can be removed from the outer housing by depressing the projection(s) so as to disengage the opening(s), enabling the spring retainer to be pulled out the rear end of the outer housing.
If desired, a mounting element that mounts the connector on the panel can also be provided. This can be accomplished in one embodiment by providing the mounting element in the form of an elongate fastener passing transversely through the outer housing and out one side wall thereof for engaging an opening through the panel, and by providing the spring retainer with a recess through which the elongate fastener extends such that the spring retainer may be removed with the fastener installed. However, the spring retainer may also be configured to allow its removal with the fasteners installed.
The mounting element preferably has a pair of the elongate fasteners that pass through the outer housing for engaging a pair of holes in the panel. Alternatively or additionally, the mounting element can include a pair of protrusions formed integrally with the outer housing for engaging openings in the panel. The protrusions can be split so that they resiliently snap into the openings in the panel.
To facilitate optimization of the concentricity angle of the ferrule, the ferrule holder preferably includes a concentricity alignment feature formed thereon in a predetermined location with respect to a measured concentricity angle of an optical fiber mounted in the ferrule. The inner housing includes a cooperative alignment feature that is engaged by the concentricity alignment feature on the ferrule holder when the ferrule holder is rotated about a central longitudinal axis thereof so as to circumferentially align the alignment features. In this manner, the measured concentricity angle of the optical fiber is located in a predetermined direction with respect to the inner housing. The alignment features preferably comprise a slot formed in one of the ferrule holder and the inner housing and a key formed on the other of the ferrule holder and the inner housing for engaging the slot. Preferably, the alignment features are structured and arranged so that the ferrule holder can be mounted in the inner housing in only one position. Accordingly, the concentricity angle of the ferrule can be optimized.